Wat. Code, § 12580

It is further declared that the State should engage in the study and coordination of all water development projects, including flood control projects, undertaken by counties, cities, state agencies and public districts, and the United States or any of its departments or agencies in order that such allocations and appropriations as are made by the State Legislature for such purposes will be expended upon those projects which are most beneficial to the State, and which will bring maximum benefits to the people of the State from the expenditure of public funds, and also that the State should participate in the construction of flood control works and projects and render beneficial aid thereto, when the benefits are in excess of the estimated cost.